it says i can use other formats, but only if i let it convert through amazon. Now I know, that I sure can convert it my own with software tools, but can't the paperwhite and kindle 4, touch, so the newer ones use those formats native.

The page says png, jpg I need to convert too. I found that I must create an ordner named images and then the files appear. Maybe I need to create another folder with a name I don't know and the kindle shows the other formats too. For example a htm page, .doc?

The Kindle 2 added native PDF capability with the Version 2.3 firmware upgrade.[22] Earlier versions could not generally read PDF files, but Amazon provided "experimental" conversion to the native AZW format,[95] with the caveat that not all PDFs may format correctly.[96] The Kindle 2 added the ability to read the Audible Enhanced (AAX) format, but dropped the ability to read Audible versions 2 and 3. The Kindle 2 can also display HTML files stored on the unit.

The fourth/fifth generation Kindles, Kindle Touch, Kindle Touch 3G, and Kindle Paperwhite can display AZW, TXT, PDF, unprotected MOBI, and PRC files natively. HTML, DOC, DOCX, JPEG, GIF, PNG, and BMP are usable through conversion. The Touch and Touch 3G can also play Audible Enhanced (AA, AAX) and MP3 files.[97] Amazon indicated in 2012 that the fourth generation Kindles will be updated to support the KF8 format.[98]
Email conversion

Amazon offers an email-based service that will convert GIF, PNG and BMP graphics to AZW.[99] Amazon will also convert HTML pages and Microsoft Word (DOC) documents through the same email-based mechanism, which will send a Kindle-formatted file to the device via 3G for $0.15 per MB or via WiFi for free. These services can be accessed to Kindle devices, Apple iOS devices running Kindle app version 2.9 or greater, and Android devices running Kindle app version 3.5 or greater.[100]

I asked if this is correct! I am not sure, because the text says the same about the picture formats, that they need to be converted, but they work native, when put in a folder called images.

And in the description of the reader on various sites they say HTML, DOC, DOCX, AZW3, AZW, TXT, PDF, MOBI, PRC nativ. So why should they mention HTML, DOC, DOCX as useable formats, when they need to be converted?

When I convert things, then it would for example view epub too. Just need to convert them. And the kindle views pdf and txt files, so it is not too far away that it would do that with the others too. And this was the only concrete information source I found on it till now. So I'm not too sure if it is true.

Maybe they too need to be put in a special folder, or something else need to be done to easily display them on the reader.

Because HTML, DOC, DOCX, JPEG, GIF, PNG, and BMP are usable through conversion only, and always have been available only through conversion. Those are the only formats that the Amazon email service handles. .mobi and .pdf, and .txt are the only formats read natively that are supported officially. If you got /images to work, good for you, but it isn't documented to work, and they could do an update and take away that capability.